The long-term objective of this project is to establish the mechanism by which catecholamine biosynthesis is regulated. It may provide some of the basic knowledge necessary for a rational approach to certain cardiovascular diseases such as hypertension and to some psychiatric problems, such as the affective disorders. We are particularly interested in studying the molecular mechanism of the feedback control and all the processes that in one way or another modify catecholamine biosynthesis or change the effectiveness of catecholamines at the receptor level such as supersensitivity and tachifilaxis. The studies on dihydropteridine reductase will be continued in order to establish the importance of this enzyme in the regulation of catecholamine biosynthesis. Further studies of the immunochemical localization of the enzyme in different organs are planned.